The conventional power-factor regulating apparatus for three phase circuit is composed of delta-connected condensers 1a'1b'1c', series reactors 2a'2b'2c', and V-connected discharging coils 3a 3b shown in FIG. 1.
The apparatus is connected to a distribution line through a switch 4 sychronized with a switch 4' for connecting a load L to the distribution line.
Said discharging coils 3a 3b are provided for the purpose of discharging the condensers 1a'1b'1c' within a predetermined time while said load is disconnected from the line in order to absorb impulse waves which might arise in the circuit caused by differences between line voltages and electric charge remaining on the condensers. However, the coils can't absorb said impulse waves completely.
It is incidentally noted that devices or apparatuses which produce impulsive noise sometimes generate in nearby computers harmful effects such as transformation of content of memories with the impulsive noises despite provision of discharging coils. Such harmful effects are particularly serious for important memories such as financial data.
Furthermore, the operating term of said discharging coils, from approximately a few seconds to a few minutes, is too long in the case where rapid switching is needed, when the coils overwork and destroy themselves because of the rapid switching synchronized with the switching for said load.